Abstract
Cognitive states like motor imagery (MI; simulating actions without overtly executing them) share a close correspondence with action execution, and hence, activate the motor system in a similar way. Unlike external objects, the mental rotations of one’s own hand are strongly influenced by the same motor rules and anatomical constraints that shape real movements. In view of these anatomical constraints, response times are longer for hands presented at awkward orientations (i.e., 90° lateral and 180°) and from the palm view. Conversely, hands presented in more manageable orientations (i.e., 0° and 90° medial) from back views generate the fastest responses. Palm-view stimuli are processed by similar brain regions involved in motor simulation and execution, while back-view stimuli are thought to be processed by visual areas of the brain. This supposed shift in strategy offers that when viewing back-hand stimuli, participants employ visual strategies generating the fastest responses, whereas palm-hand stimuli employ motoric strategies resulting in longer recognition times. Using the hand laterality judgment task, fifty younger adults mentally simulated hands displayed from two different viewpoints (palm and back) and in four different orientations: 0°, 90°medial, 90° lateral, and 180°. Results indicated that the fastest transformations of hands occurred at 0° and 90°M without differences between these two orientations, while the slowest hand transformation occurred at 90°L and 180°. The comparison between back and palm views revealed longer response times when hands were shown from the palm view. Results suggest that when shown palm-view stimuli, participants process hands as body parts rather than external objects. In other words, participants mentally rotate their own hands into the orientation of the visually presented hand, eliciting an implicit motor strategy. Taking this into account, it is suggestive that internal motor representations have an important role in motor planning and execution that govern real-world hand movements.